The Dual Role of Bacillus sp. KKU-RE-018 Isolated from Medicinal Plants in Controlling Anthracnose Disease and Enhancing the Growth of Chili Plants

Chili (<i>Capsicum annuum</i> L.) is a herbaceous vegetable grown and consumed worldwide. In Thailand, chili plants are severely hampered by anthracnose disease, leading to severe yield losses. This study aimed to investigate endophytic bacteria (EPB) for their potential as a biocontrol agent and plant growth promoter (PGP). Among a total of 108 isolates, strain KKU-RE-018 was identified by partial 16S rRNA gene sequencing as belonging to the genus <i>Bacillus</i>. This isolate exhibited strong antifungal activity against <i>Colletotrichum capsici</i>; its activity occurred through the production of hydrolytic enzymes, including chitinase and β-1,3-glucanase, and exhibited PGP properties. This endophytic bacterium significantly reduced anthracnose severity compared with the control, achieving a disease reduction index (DRI) of over 60%. Moreover, chili plants treated with the bacterium showed higher plant growth parameters under greenhouse conditions. The levels of phenolic compounds and salicylic acid in plants treated with <i>Bacillus</i> sp. KKU-RE-018 could activate systemic acquired resistance (SAR). Taken together, these findings demonstrate that <i>Bacillus</i> sp. KKU-RE-018 plays a multifaceted role, capable of suppressing anthracnose and simultaneously promoting chili growth.